Enhanced localized electron density from PdCu nanoparticle loading on a defective TiO2 support for selective nitrate electroreduction to ammonia

Abstract

The electrocatalytic nitrate (NO₃⁻) reduction reaction (NITRR) to synthesize ammonia (NH₃) offers a promising method for both pollution abatement and chemical production. However, the sluggish multi-electron/proton-involved steps limit ammonia selectivity and yield. Herein, we loaded PdCu nanoparticles (PdCu NPs) onto defective TiO₂ to regulate the localized electron density for selective NH₃ synthesis. Our results show a significant increase in NH₃ yield and selectivity (112.0 to 322.7 μmol cm⁻² h⁻¹ and 34.6 to 80.1%, respectively), induced by the introduction of PdCu NPs. Importantly, in situ and operando investigations combined with density functional theory (DFT) calculations reveal that PdCu NPs enhance the localized electron density at oxygen vacancies. This regulated electron density suppresses N–N coupling and accelerates N–H bonding processes, thus modulating NH₃ selectivity. This unique insight based on localized electron density control provides a rational design strategy for metal-defect support catalysts in ammonia production using electrochemical processes.